902 conditions and with varying clay contents and qualities. This testing confirms the metallurgical and geotechnical moisture requirements for the construction of the dam or paddock, validating the geotechnical requirements. Controls were also made of the 200-mesh screen, apparent density, standard and modified Proctor density, and water permeability. During testing, mass and water balances are performed, along with the classification efficiency of the screen and hydrocyclones. Water removed by the overflow is also analysed, and the option to recover it using a high-compression thickener and recirculate it into the process is explored to optimize water consumption. After the pilot phase is completed, a pre-feasibility, feasibility, and detailed engineering study is conducted, along with the operational readiness of a 1000 tph industrial plant with its complete automated operation and control system, including water recovery and clean sand generation systems. This study will be evaluated for potential implementation. Even with the finest screens some of the 75 μm um material will pass to screen u/s. To minimise the losses the screen is operated with a deep bed and the screen u/s cycloned to remove fines and water with the coarse fraction returned to the screen. Typically, screen are more effective classifiers than hydrocyclones giving a sharper cut and more effective removal of undersize materials. The test arrangement is shown in figure 2. Typically, screens produce a cleaner sand because the classification efficiency of DW Screens is (65-85%) with inefficiency close to the cut size vs Hydrocyclones (45-65%) where inefficiency is entrained slimes. Clays tend to stick to coarser material exaggerating cyclone inefficiency. The critical variables were the tailings physical characterization, including PSD, clay percentage (montmorillonite and illite between 3-15%), mineralogy by XRD, and specific gravity (2.7 g/cc). operating conditions included pressure (100-150 Kpa), solids in the screen feed (68-72%), apex (1.25”-1.50”) and vortex (1.25”-1.50”). Screen characteristics included slot aperture(0.3-0.8 mm), open area percentage (30-45%), flow rate (35-45 m3/h), bed depth (10-15 cm), and fines <75 um (10-15%). The fresh feed to come from current cyclone underflow to go dewatering screen. The final product is the oversize screen and the retorn of water from the overflow hydrocyclones. Figure 3 Pilot plant arrangement
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